THE RELATIONS OF BARIUM-TUNGSTEN CATHODE PROPERTIES TO THE TUNGSTEN MATRIX STRUCTURE

Some data of emission and evaporation properties referring to the tungsten matrix structure of the impregnated cathode are analyzed. The results indicate that the particle size of tungsten powder and the pore size in the porous matrix determine the total inside surface area of all pores, the diffusion length of barium over the tungsten grain surface, and the diameter and length of path for the barium to transport through. These factors all relate to the properties and operation mechanism of an impregnated cathode; therefore, it would not be strictly right to employ only the matrix porosity for characterizing the cathode properties. Finally, the preferred structure of porous tungsten matrix depending on different applications of impregnated cathode is proposed.